The present invention relates to a method for using a water-soluble linear macroamine polymer as a flocculating or coagulating agent in clarifying, precipitating and decoloring water. More particularly, this polymer is one having at least about 65 mol percent amine content and not greater than about 23 mol percent polyene content, and a method of preparing the same. Further, it relates to a macroamine polymer in which amino groups are introduced to the polymer matrix by the reaction of one or more of certain N-monoalkylanilines with polyvinyl bromide.
A number of detailed researches have been made up to now with respect to reaction of polyvinyl chloride with a variety of compounds. However, the reactivity in these reactions is so small that it has been difficult to introduce amino groups to a satisfactory extent. For instance, when polyvinyl chloride is reacted with an amine, the degree of the introduction of the amine to the polymer matrix under ordinary reaction conditions reaches the level of only about 2.6 to 10%. See, for example, D. Hummel; "Plaste Und Kautschuk", Volume 9, No. 11, pages 532-5 (1962), East Germany. Further increase in the degree of introduction does not occur even by carrying out the reaction over longer periods of time and because the result is the promotion of the formation of polyenes by dehydrohalogenation rather than the introduction of the amine.
It has been known in the art that some inorganic-type and high molecular-type flocculating or coagulating agents are effective for use in waste water disposal.
The inorganic-type flocculating agent exhibits its activity mainly by lowering the electric charge of the surface of substance suspended in water to be disposed.
On the other hand, the high molecular-type flocculating agent exerts such functions, besides the above-mentioned function, as adsorption of suspended substance at the active site on the polymer, or by agglomeration due to cross-linking reaction, none of which can be attained upon the use of the inorganic flocculating agent alone.
Therefore, it is clear that the high molecular flocculating agent has much more advantageous features than inorganic-type one, in (a) its strong flocculating ability even when the use of less quantity and (b) its capability of forming large-sized floc.
As a result, the high molecular flocculating agent can quicken the precipitating or floating speed as well as filter-ring or drying speed, etc., and serves for shortening the requisite time of disposal and for increasing the capacity of disposal while reducing the amounts of sludges and cakes formed, to thereby contribute to the rationalization of waste water disposing procedures.
In spite of such advantageous features which might be expected to be helpful for the rationalization of disposing procedures, conventional high molecular flocculating agents are not yet satisfactory for use in waste water disposal. In case of disposing waste water containing suspended colloidal organic solids, for instance, it is generally noticed that a cationic polymer has remarkably excellent ability in clarifying activity, whereas satisfactory result has not always been obtained especially with respect to the ability of forming coarse or large-sized floc which is expected as one of inherent advantages accompanied by the use of a high molecular-type flocculating agent.
This is not essentially attributable to the nature of a cationic polymer, but to the great difficulty in the production of such a cationic polymer having a polymerization degree sufficiently high to form coarse floc.
Certain anionic and nonionic type high molecular flocculating agents with high degree of polymerization are available in the art, but they do not exhibit satisfactory effect unless they are used in combination with an inorganic-type floccuating agent.
The reason is due to the fact that anionic or nonionic type high molecular flocculating agents behave as a floc-growing agent rather than exerting the function of flocculation by the neutralization of the electric charge of suspended colloidal substance.
Other than the polymer of the present invention, we know of no high molecular flocculating agent available in the art which provides clarifying, precipitating and decoloring functions at the same time, and is capable of exhibiting remarkably excellent effect as a single agent. The clarifying and decoloring properties of conventional high molecular flocculating agents were only derived subsidiarily by the result of the agglomeration and precipitation.
Accordingly, such a conventional-type high molecular flocculating agent has a drawback such that it is almost ineffective for the decoloration of a colored system occurring due to completely dissolved substance therein.
It is a general object of the present invention to provide a method for using a macroamine polymer which is water-soluble, and has a high amine content as a flocculating or coagulating agent to remove certain impurities from water. Further objects of the present invention are to provide a method of using a macromine polymer in clarifying, precipitating and decoloring activities with respect to water.
Other and further objects, features and advantages will be apparent from the following description of the invention given for the purpose of disclosure.
The present invention is based upon the creation of a certain linear macroamine polymer, the development of a method for producing the polymer, and the discovery that the polymer is particularly useful as a flocculating agent to assist in the removal of certain material from water. The polymer has a structural unit showing by the following formula: ##EQU2## wherein R represents an alkyl group containing 1 to 4 carbon atoms, x is a mol decimal fraction between about 0.65 and 0.95, and y is a mol decimal fraction between about 0.23 and 0.04. Preferably x is between about 0.80 and 0.95 and y is between 0.23 and 0.04.
This linear macroamine polymer can be prepared by reacting polyvinyl bromide with an N-monoalkylaniline having 1 to 4 carbon atoms in the alkyl group.
The polyvinyl bromide to be used is not limited to any specific type and may be conveniently produced in accordance with conventional processes such as mass polymerization, emulsion polymerization, solution polymerization and photo polymerization. The polyvinyl bromide usually will have a molecular weight ranging from about 1,000 to 300,000, and preferably between about 10,000 and 150,000.
The preferred N-monoalkylaniline is N-methylaniline.
The macroamine polymer of the present invention may be prepared by mixing the polyvinyl bromide and the N-monoalkylaniline and stirring the reactants while heating under an atmosphere of an inert gas such as nitrogen or argon. The reaction of the polyvinyl bromide with the N-monoalkylaniline is usually carried out at temperatures ranging from 80.degree. to 250.degree. C., preferably between about 120.degree. and 180.degree. C., for a period of a few minutes up to 24 hours, preferably from 5 to 15 hours. The reaction proceeds well at atmospheric pressure although superatmospheric conditions may be used if desired.
The N-monoalkylaniline not only participates in the reaction as an aminating agent, but also serves as an excellent solvent for the polyvinyl bromide. The polyvinyl bromide dissolves in the N-monoalkylaniline promptly after it has been added, and the reaction takes place readily when the resulting mixture is heated.
If desired, the reaction can be carried out in the presence of polar solvents such as tetrahydrofuran, dioxane, dimethylformamide, diethylforamide and dimethyl sulfoxide.
The quantity of N-monoalkylaniline which should be used is more than the chemical equivalent to the polyvinyl bromide and preferably about 3 to 20 times greater than that equivalent. The use of greater amounts of alkylaniline does not cause deterioration of the reaction, but is wasteful. On the other hand, the use of an alkylaniline below the chemical equivalent of the polyvinyl bromide is not desirable since it does not create sufficient amination of the polyvinyl bromide and requires a greater amount of solvent.
After the reaction of the polyvinyl bromide with the N-monoalkylaniline has been carried out to the desired extent, the resulting macroamine polymer can be separated from the unreacted alkylaniline in an appropriate manner. For instance, the polymer is separated from the remaining constituents by adding to the reaction products an inert material in which the polymer is insoluble, but in which the other materials are soluble. Examples of this material are ethyl acetate, isopropyl acetate, ethyl ether, petroleum ether, isopropanol, n-butanol, acetone, diethyl ketone and methyl ethyl ketone. This will result in a precipitation of the polymer which may be subsequently recovered by filtration. The precipitated polymer may be purified, if desired, by washing with alkali and thereafter rinsing with water and drying.
The macroamine polymer thus produced contains a large proportion of the alkylaniline. It has been found when the mol percent of the alkylaniline in the polymer reaches at least about 65%, that the macroamine polymer becomes water soluble. The macroamine polymer, when it is used as a flocculating agent, needs to be soluble in water so that it will easily dissolve in industrial waste water and other aqueous bodies upon its addition thereto and be able to combine with dissolved or suspended substances in the waste water to effect clarification, precipitation and decolorization, and finally settle them from the water.
If the macroamine polymer has less than about 65 mol percent alkylaniline, the polymer is insoluble in water and does not function satisfactorily as a flocculating agent. When the amount of alkylaniline is between about 80 and 95 mol percent, the polymer exhibits excellent results in the clarifying, precipitating or decoloring activity.
The water-soluble macroamine polymer of the present invention reacts readily with metallic ions such as sodium, potassium, magnesium, calcium, aluminum, copper, silver, gold, zinc, cadmium, mercury, titanium, tin, lead, chromium, molybdenum, manganese, iron, cobalt, nickel, platinum, etc. and promptly forms a precipitate with them. Although we do not completely understand the mechanism of the reactions of this macroamine polymer with metallic ions, we believe that what occurs is that these cationic substances form chelates with the macroamine polymer.
Also, in an acidic solution, this macroamine polymer will react with some anionic substances and form precipitates. Here again, the exact nature of the precipitate or the reactions that occur is not known, but it is thought that the precipitates are salts, complexes or cross-linked products.
Since these salts, complexes, cross-linked products and chelates are insoluble in water, they precipitate as they form, and thereby remove suspended or dissolved substances from the water.
If desired, the polymer can be regenerated from the reaction product of the polymer with the cations by dissolving the reaction product in an acidic aqueous solution (pH between about 1 and 5), preferably having a pH between about 1 and 3.
The macroamine polymer of this invention has both a high molecular weight and a high content of the amino group, and as a result the polymer serves as a flocculating agent with even minor concentrations of cations. It, therefore, is particularly useful for the treatment of various types of waste water, drainage or other aqueous solutions.